Results taken during Curiosity's eight-month cruise to Mars indicate that astronauts would receive a radiation dose of about 660 millisieverts during a 360-day roundtrip flight, the fastest travel possible with today's chemical rockets. That dosage does not include any time spent on the planet's surface. A millisievert is a measurement of radiation exposure.
NASA limits astronauts' increased cancer risk to 3 percent, which translates to a cumulative radiation dose of between about 800 millisieverts and 1,200 millisieverts, depending on a person's age, gender and other factors.
20:08 Month in Space: November 20169